Re: [Chicken-users] Question again on heap mutation from signal handlers.

[Jörg F . Wittenberger]

On Oct 2 2011, Jörg F. Wittenberger wrote:

> Kon (or maybe Felix)
>
> On Sep 1 2011, Kon Lovett wrote:
>
> > Probably of no use to you but … When I added all the extra unix
> > (Chicken v2 I think) signals stuff I figured (ha) that a Scheme
> > signal handler could only perform operations that accessed existing
> > structures, no heap mutation. I used handlers that basically only
> > set flags.
>
> Is there a way to verify that signal handlers can not allocate
> on the heap?
>
> As far as I understand runtime.c this should be true.
> But it's fairly complicated to reason here.
> It would be very, very helpful to be sure about that one.
>
> Since my eat-all-mem issue was gone all too suddenly ...
> Now I tried to re-enable the old handler invocation to confirm
> that the old issue would come back.
> So far it did not - which is confusing.

To summarize: no reason for confusion: "so far" meant: about 20
min. trying to force it.  Sometimes it's easier to just wait :-/

At least it reduces confusion.  A bit, that is.

If I could knew for sure that signal handlers may not touch the heap,
I would know that the approach to accept the higher latency in exchange
for the more natural coding of signal handlers would be worth the
time.

Alan: DON'T enable the normal signal handling.  It might work some
seemingly infinite time.  But eventually goes into EAM mode.
No theory why; just observation so far.

/Jörg


PS: If it eventually turns out to be true that the signal handler
has been the issue I had.  Plus it would turn out to be verifiable
that always running with interrupts disabled does not eventually
harm normal behaviour.  ...  THEN I'd call that a productive time!
We could leave quite some code with the garbage collector.